In neuropsychological research, a link has been made between substance dependence and deficits in frontal system (i.e. executive) functioning, including problems with decision-making, working memory, and impulse control. In behavioral research, a link has been made between self-reported executive function deficits (e.g. impulsivity, sensation seeking, myopia) and HIV risk behavior. However, little if any research has been conducted to bridge the gap between neuropsychological and behavioral research. A better understanding of how neurocognitive factors influence HIV risk-behavior is critical to prevention efforts, as these factors may be working against specific intervention strategies or moderating intervention effectiveness. However, many behavioral interventions focusing on the intersection of substance use and sexual risk-taking do not consider neurocognitive factors, even as they target symptoms related to them (e.g. poor decision- making, problems with impulse control). The current proposal is designed to examine the role of neurocognitive factors in determining HIV risk behavior among men who have sex with men (MSM). Specifically, the proposed project aims to: 1) Investigate the role of neurocognitive deficits in the relationship between drug use and sexual risk-taking among substance using MSM;2) Examine whether the interactions among different neurocognitive deficits (e.g. hypersensitivity to reward vs. poor response inhibition) are associated with different patterns of relationship between substance use and HIV risk behavior;3) Identify dispositional and contextual correlates that may promote or inhibit risk-behavior among individuals with particular neurocognitive profiles;and 4) Investigate the interaction between neurocognitive and dispositional factors in determining risky decision-making in the context of an experimental manipulation designed to increase reliance on the emotional "go" system. The proposed project will enroll 200 sexually active, substance using MSM. We will stratify the sample along two dimensions: HIV-status and risk-taking behavior. All participants will complete: a) a neuropsychological test battery designed to assess decision-making deficits and overall cognitive functioning;b) a self-report survey designed to assess dispositional and contextual factors that might impact risky decision- making;and c) a laboratory based real-time decision-making task in the presence or absence of an experimental manipulation. Our research design was developed to provide a nuanced understanding of the interaction between neurocognitive, dispositional, and contextual factors in determining HIV risk behavior among MSM, and will be critical to the development and adaptation of HIV prevention interventions for this population. PUBLIC HEALTH RELEVANCE: This project investigates the synergistic relationship among neurocognitive, dispositional, and contextual factors in HIV risk behavior. A better understanding how of neurocognitive factors impact substance use and HIV risk is critical to the development, implementation, and adaptation of effective HIV prevention efforts.